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If your doctor suspects that you have a brain or spinal cord tumor after conducting a thorough medical and neurological exam, you will be referred to specialists who can perform imaging tests, such as X-rays and MRI scans, and laboratory tests. Understanding these tests and what the results mean will help you make a better decision about how to treat your illness.

Imaging tests used to diagnose brain tumors include:

CT scans

MRI

PET scans

Diagnosing Spinal Cord and Brain Tumors: CT Scans

Computerized tomography (CT) scans, also called CAT scans, use X-rays to create a computerized image of the body. For the scan, the patient lies flat on a table that slides into a doughnut-shaped scanner. The scanner circles the head or spine, allowing X-rays to penetrate from all directions. When complete, the computer transforms the thousands of thin, cross-sectional readings into an image. For better images, your doctor may choose to inject a contrast dye before scanning.

"CAT scans are one of the most common tests we use," says Paul Graham Fisher, MD, associate professor of neurology and pediatrics and director of neuro-oncology at Packard Children's Hospital in Palo Alto, Calif. "They are quick, easy, and readily available."

Diagnosing Spinal Cord and Brain Tumors: MRI Scans

Magnetic resonance image (MRI) scanners take images of the brain and spinal cord from another tunnel-shaped machine, but rather than using X-rays, they use a large magnet and radio waves to capture an image of the body. As with the CT scan, your doctor may choose to inject a contrast dye before scanning.

"This is another common test," says Dr. Fisher. "If the case is a 'need to know now,' an MRI is the test I would use." MRIs are the most sensitive imaging test currently available in standard medical practice, providing clearer pictures of soft-tissue areas than CT scans.

Diagnosing Spinal Cord and Brain Tumors: PET Scans

PET scans, or positron emission tomography scans, are taken after tiny amounts of a radioactive material, called a tracer, are inhaled, swallowed, or injected in the body. Rather than reveal the structure of the brain or spinal cord, they show how the tissues are working. PET scans and MRIs are sometimes combined to produce detailed views of the body, called image fusion or co-registration. PET scans are not routinely used to diagnose primary brain tumors, or brain tumors that started in the brain, but can be used to diagnose low-grade tumors and check for tumor recurrence.

Other Tests Used to Diagnose Spinal Cord and Brain Tumors

Magnetic Resonance Spectroscopy. An MRS lets doctors take a chemical snapshot of tissue using an MRI scanner. Like PET scanning, it is useful in diagnosing low-grade tumors and tumors that reoccur following treatment.

Arteriography. Also called angiography, an arteriography is an X-ray that outlines the inside of the arteries using a contrast dye. It is generally used for brain and spinal cord tumors only to determine their actual location for surgery.

Biopsy. With this test, the doctor removes a tiny piece of tissue from the spine or brain for examination under a microscope. For brain tumors, a small, narrow hole is drilled into the skull so that a needle can be inserted to withdraw tissue.

Lumbar puncture. Also called a spinal tap, a lumbar puncture is a test in which the doctor inserts a thin needle between the bones of the spine to withdraw spinal fluid. Examining the fluid determines whether cancer cells are present.

Blood and urine. These tests are routinely conducted before other tests to determine how well your body is functioning.

If you recieve a spinal cord tumor or brain tumor diagnosis, these same tests may be used throughout your treatment and follow-up care to monitor your progress.